Addresses reviewer feedback: the new Swift behaviors (implicit imports,
constructor fallback, extension dedup, export detection) had no dedicated
integration tests. Adds 4 fixture directories and 11 new test assertions:
1. swift-implicit-imports: two files, no explicit import, cross-file
constructor + member call resolves via addSwiftImplicitImports
2. swift-extension-dedup: extension creates duplicate Class node,
constructor still resolves to primary definition
3. swift-constructor-fallback: ClassName() without `new` resolves as
constructor via free→constructor retry
4. swift-export-visibility: internal symbols visible cross-file,
public/open visible, private/fileprivate noted as Tier 3 limitation
All 3,603 tests pass (11 new, 0 regressions).
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
